Drilling waste management is one of the most important challenges in the petroleum industry. The used drilling mud and cuttings result in a substantial ecological contamination problem after drilling is completed. The main pollution of cuttings is caused by biocides; oil; completion or stimulation fluid components; corrosion inhibitors; reservoir fluids (crude oil, brine); inorganic cations and anions, and drilling mud chemical components. The compositions and methods described herein are effective for solidification and remediation of drilling muds and cuttings containing any or all of these pollutants; and agricultural wastes containing animal excrement and/or agricultural fertilizer run off.
The current way of drilling waste management remains somewhat crude from the ecological point of view. The drilling wastes are mainly collected in tanks or pits near the drilling rig and sometimes, after some initial treatment, are either dumped or buried when drilling is halted or mixed with the nearby ground soil and buried.
One of the most popular methods of drilling waste treatment is solidification and stabilization. If a pollutant is below the allowed limit, drilling waste can be solidified in place. Cement and silica are the most popular agents. Von Krosigk U.S. Pat. Nos. 6,835,697; 6,809,067; and published application US 2002/169082 A1 and 2002/169084 A1 disclose adding a number of materials to the drilling waste in a high shear mixer, particularly a solidification agent, such as calcium oxide, Portland cement or an ash product, together with a cellulose additive and a cell transport additive, such as an electrolyte enzyme. The cementing technique encapsulates the contaminants and minimizes the mobility of the contaminants out of the resulting encapsulated drilling waste material, and cements the contaminants in place.
Other solidification materials include dehydrated limestone; coke ash (U.S. Pat. No. 7,059,805); Portland cement and spherical zeolite (U.S. 2005/133222); fly ash (U.S. Pat. No. 5,383,521); and blast furnace slag (U.S. Pat. No. 5,058,679). The solidifying additives require at least eight (8) hours to achieve sufficient solidification to pass a critical Paint Filter Test (US EPA 9095B) and the US EPA Toxic Characteristic Leachate Procedure (US EPA 1311), that is used to determine that the solidified waste will not release contaminated liquid. These solidifying additives also require a much higher percentage of additives and, therefore, add significantly more mass and weight to the contaminated material resulting in more costly/and fill disposal.
Solidifying liquid drilling waste has tremendous benefits for oilfield drilling applications, environmental safety/clean up applications, and drilling companies. The benefit for environmental safety is that it can confine permanently most heavy/toxic metals and some toxic organics inside a solid matrix. Therefore, heavy metal ions and organic toxic and/or hazardous compounds will not leach out and cause environmental issues on local land and water. For oilfield drilling applications, replacing liquid waste with solid waste results a huge economical benefit. A significant portion of the drilling costs is in remediation of the sites and disposing of the waste generated during drilling operations. About 20-30% of the drilling cost is currently used for waste disposal because the drilling companies' costs are extremely high when expensive vacuum trucks are required to haul the liquid wastes away to far-away landfill sites. Much less expensive dump modes of transport can be used if the waste is in solid form so long as the solid waste passes the Paint Filter Liquids Test (PFT). Additionally, the solid waste can even be disposed of locally if it passes the Toxicity Characteristic Leach Procedure (TCLP), which further reduces the cost of waste disposal. The benefit for environmental safety is that it can permanently fixate heavy/toxic metals and the majority of toxic organics inside the solid matrix. Therefore, heavy metal ions and organic toxic compounds will not leach out and cause environmental issues in local non-hazardous land fills.
Another benefit of this invention is the solidification of the liquid wastes with the layered phyllosilicate and superabsorbent polymer allows the evaporation of water from the solidified waste. By allowing the evaporation of water, two benefits are realized. First, the volume and mass of the solid waste reduces and this reduces the transportation volume and cost. Second, the contaminants of concern are less likely to leach out of the solidified solid waste as the water evaporates as the solidification becomes tighter.